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Resources
Chapter Presentation
Transparencies
Visual Concepts
Standardized Test Prep
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Chapter 48
Digestive and Excretory Systems
Table of Contents
Section 1 Nutrients
Section 2 Digestive System
Section 3 Urinary System
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Chapter 48
Section 1 Nutrients
Objectives
• Relate the role of each of the six classes of nutrients in
maintaining a healthy body.
• Describe each of the parts of the USDA Food Guide Pyramid.
• Identify foods containing each of the organic nutrients.
• Explain the importance of vitamins, minerals, and water in
maintaining the body’s functions.
• Identify three disorders associated with improper nutrition.
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Chapter 48
Section 1 Nutrients
Six Classes of Nutrients
• Some organisms must obtain energy from
nutrients in the food they consume.
– A nutrient is a substance required by the body
for energy, growth, repair, and maintenance.
• All foods contain at least one of the six basic
nutrients, and some can contain more.
– The six basic nutrients are carbohydrates,
proteins, lipids, vitamins, minerals, and water.
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Chapter 48
Section 1 Nutrients
Types of Nutrients
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Chapter 48
Section 1 Nutrients
Six Classes of Nutrients, continued
• Nutritionists classify foods into six groups.
– These six groups are: meat, milk, fruits,
vegetables, breads/cereals, and
fats/oils/sweets.
• The USDA Food Guide Pyramid shows the
number of servings from each food group needed
for a balanced diet.
• Nutrients provide energy for powering cellular
processes.
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Chapter 48
Section 1 Nutrients
USDA Food
Pyramid
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Chapter 48
Section 1 Nutrients
Carbohydrates, Proteins, and Lipids
• The three nutrients needed by the body in the
greatest amounts are carbohydrates, proteins,
and lipids.
– All of these nutrients are called organic
compounds, which are compounds that
contain the elements carbon, hydrogen, and
oxygen.
• An example of a carbohydrate is pasta; an
example of a protein is chicken; and an example
of lipids is olive oil.
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Chapter 48
Section 1 Nutrients
Nutrients in Food
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Chapter 48
Section 1 Nutrients
Carbohydrates, Proteins, and Lipids,
continued
• Carbohydrates
– Carbohydrates are organic compounds
composed of carbon, hydrogen, and oxygen
that provide nutrients to the cells of living
things.
– Carbohydrates contain sugars that can
quickly be converted into usable energy.
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Chapter 48
Section 1 Nutrients
Carbohydrates, Proteins, and Lipids,
continued
• Carbohydrates, continued
– Carbohydrates can be monosaccharides, disaccharides,
or polysaccharides.
• Monosaccharides are simple sugars.
• Disaccharides are sugars that consist of two
chemically linked monosaccharides.
• Polysaccharides are complex molecules that consist
of many monosaccharides bonded together.
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Chapter 48
Section 1 Nutrients
Carbohydrates, Proteins, and Lipids,
continued
• Proteins
– Proteins are organic compounds that are
made of one or more chains of amino acids
and are a principle component of all cells.
– Most proteins come from animal products
such as eggs, milk, fish, and beef.
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Chapter 48
Section 1 Nutrients
Carbohydrates, Proteins, and Lipids,
continued
•
Lipids
– Lipids are nonpolar molecules that are insoluble in
water and can be found in fats, oils, and waxes.
– Lipids are used to make cell membranes and hormones
and to store energy.
– The most common fat is called a triglyceride.
Triglycerides can be used for energy and to build
membranes and other cell parts.
– Fats are used in many ways throughout the body but
can be harmful if eaten in excess.
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Chapter 48
Section 1 Nutrients
Carbohydrates, Proteins, and Lipids,
continued
• Lipids, continued
– Fats can either be saturated or unsaturated based
on which fatty acid they contain.
• Saturated fats contain saturated fatty acids.
Saturated fatty acids contain carbon atoms
attached to each other with a single bond.
• Unsaturated fats have unsaturated fatty acids.
Unsaturated fatty acids have at least one
double bond between carbon atoms.
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Chapter 48
Section 1 Nutrients
Vitamins, Minerals, and Water
• Vitamins, minerals, and water are nutrients that
do not provide energy but are required for proper
functioning of the body.
• Vitamins are organic compounds that participate
in chemical reactions by helping to build various
molecules in the body.
• Minerals are nutrients that are inorganic
compounds and are necessary for certain body
processes.
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Chapter 48
Section 1 Nutrients
Vitamins, Minerals, and Water, continued
• Vitamins
– Vitamins work as coenzymes to enhance
enzyme activity.
– A diet should include vitamins because they
cannot usually be made in the body. An
exception to this is vitamin D.
– Vitamins can dissolve in water or fat.
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Chapter 48
Section 1 Nutrients
Vitamins
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Chapter 48
Section 1 Nutrients
Food Sources of Vitamins
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Chapter 48
Section 1 Nutrients
Vitamins, Minerals, and Water, continued
• Minerals
– Minerals are used to make certain body
structures, to carry out normal nerve and
muscle function, and to maintain osmotic
balance.
– Minerals can come from plants we eat directly
or the plants other animals eat.
– Minerals are released out of the body through
urine and by perspiration.
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Chapter 48
Section 1 Nutrients
Food Sources of Minerals
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Chapter 48
Section 1 Nutrients
Vitamins, Minerals, and Water, continued
• Water
– Water, which is a main component in blood,
helps to transport gases, nutrients, and wastes
throughout the body.
– Water also is a reagent in some of the body’s
chemical reactions.
– Water also helps regulate body temperature by
absorbing and distributing the heat released in
cellular reactions.
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Chapter 48
Section 1 Nutrients
Sources of Water Balance in Humans
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Chapter 48
Section 2 Digestive System
Objectives
• List the major organs of the digestive system.
• Distinguish between mechanical digestion and
chemical digestion.
• Relate the structure of each digestive organ to its
function in mechanical digestion.
• Identify the source and function of each major
digestive enzyme.
• Summarize the process of absorption in both the
small and large intestine.
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Chapter 48
Section 2 Digestive System
The Gastrointestinal Tract
• The process of breaking down food into
molecules the body can use is called digestion.
• Digestion occurs in the gastrointestinal tract, or
digestive tract, which is a long tube which begins
at the mouth and winds through the body to the
anus.
• Organs next to the digestive tract also aid in the
digestion of food through the secretions that
they produce.
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Chapter 48
Section 2 Digestive System
Digestive System in the Human Body
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Chapter 48
Section 2 Digestive System
Anatomy of the Human Digestive System
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Chapter 48
Section 2 Digestive System
The Mouth and Esophagus
• Digestion includes
the mechanical and
chemical breakdown
of food into nutrients,
the absorption of
nutrients, and the
elimination of waste.
• Digestion begins in
the mouth with the
first bite of food.
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Chapter 48
Section 2 Digestive System
The Mouth and Esophagus, continued
• Mouth
– Mechanical digestion begins when the teeth
cut and grind food.
– The tongue also aids in mechanical
digestion by keeping the food between the
chewing surfaces of the teeth.
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Chapter 48
Section 2 Digestive System
The Mouth and Esophagus, continued
• Mouth, continued
– Saliva is produced by the salivary glands to
begin chemical digestion of food.
• Saliva is a mixture of water, mucus, and a
digestive enzyme called salivary
amylase.
• Salivary amylase is the chemical in saliva
that begins the chemical digestion of
carbohydrates by breaking down certain
starches into maltose.
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Chapter 48
Section 2 Digestive System
The Mouth and Esophagus, continued
• Esophagus
– The ball of food is then forced by
swallowing action into the pharynx.
– The pharynx is an open area that begins at
the back of the mouth, and serves as a
passageway for both air and food.
– The ball of food is then forced from the
pharynx into the esophagus.
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Chapter 48
Section 2 Digestive System
The Mouth and Esophagus, continued
• Esophagus, continued
– The esophagus has two
muscle layers and by
alternating contractions
between these muscle layers,
the ball of food can be pushed
into the stomach.
• This series of alternating
rhythmic muscular
contractions and
relaxation is called
peristalsis.
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Chapter 48
Section 2 Digestive System
Peristalsis
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Chapter 48
Section 2 Digestive System
Stomach
• The stomach is an
organ involved in
both mechanical
and chemical
digestion.
• It is located in the
upper left side of
the abdominal
cavity, just below
the diaphragm.
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Chapter 48
Section 2 Digestive System
Stomach, continued
• Mechanical Digestion
– The stomach has three layers of smooth
muscle—a circular layer, a longitudinal layer,
and a diagonal layer.
– These muscles churn the food within the
stomach and help to carry out mechanical
digestion.
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Chapter 48
Section 2 Digestive System
Stomach, continued
• Mechanical Digestion, continued
– The inner lining of the stomach is a mucous
membrane that is composed of epithelial cells
and openings called gastric pits.
– Gastric pits are the open ends of gastric
glands that release secretions into the
stomach.
– These secretions form the acidic digestive
fluid that digests food in the stomach.
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Chapter 48
Section 2 Digestive System
Mechanical Digestion
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Chapter 48
Section 2 Digestive System
Stomach, continued
• Chemical Digestion
– Gastric fluid carries out chemical digestion in
the stomach.
• Gastric fluid is a liquid that is secreted by
the gastric glands in the stomach.
– Hydrochloric acid within the gastric fluid helps
dissolve food and minerals and keep bacteria
at bay.
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Chapter 48
Section 2 Digestive System
Stomach, continued
• Chemical Digestion, continued
– Mucus secreted in the stomach forms a
coating that protects the lining of the stomach
from hydrochloric acid and other digestive
enzymes.
– An ulcer will result if the mucous layer is
absent from the stomach lining.
• An ulcer is a lesion of the surface of the
skin or a mucous membrane of the
stomach.
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Chapter 48
Section 2 Digestive System
Chemical Digestion
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Chapter 48
Section 2 Digestive System
Stomach, continued
• Formation of Chyme
– After food enters the stomach, it closes by
way of the cardiac sphincter.
• The cardiac sphincter is a circular muscle
located between the esophagus and the
stomach.
– While closed, the stomach churns to break up
the food and mixes it with the gastric fluid.
This process forms a mixture called chyme.
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Chapter 48
Section 2 Digestive System
Stomach, continued
• Formation of Chyme, continued
– Peristalsis forces the chyme into the small
intestine from the stomach.
– The pyloric sphincter controls the amount of
chyme that enters the small intestine from the
stomach.
– Digestion in the stomach is also aided by other
organs near the stomach.
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Chapter 48
Section 2 Digestive System
The Liver, Gallbladder, and Pancreas
• The other organs that help digestion are the liver,
gallbladder, and pancreas.
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Chapter 48
Section 2 Digestive System
The Liver, Gallbladder, and Pancreas,
continued
• Liver
– The liver performs numerous function in the
body including storing glucose, making
proteins, and breaking down toxic substances.
– The liver produces bile, which is vital to
digesting fats.
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Chapter 48
Section 2 Digestive System
The Liver, Gallbladder, and Pancreas,
continued
• Gallbladder
– After the liver produces bile it travels through a
Y-shaped duct to the gallbladder.
– The gallbladder is a saclike organ that stores
and concentrates bile.
– The gallbladder releases the bile through a
common bile duct into the small intestine.
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Chapter 48
Section 2 Digestive System
The Liver, Gallbladder, and Pancreas,
continued
• Pancreas
– The pancreas is an organ that lies behind the stomach.
The pancreas serves two roles in its part in the digestive
system.
• The first role it plays is to increase the pH of the
stomach acid by producing sodium bicarbonate.
• The second role it plays is to secrete enzymes that
help to further break down carbohydrates, proteins,
lipids and nucleic acids.
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Chapter 48
Section 2 Digestive System
Small Intestine
• The small intestine
includes three
sections—the
duodenum, the
jejunum, and the
ileum.
• The chyme from the
stomach will further
break down in the
small intestine.
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Chapter 48
Section 2 Digestive System
Small Intestine, continued
• Absorption
– Absorption occurs mostly in the small
intestine. Absorption occurs when the end
products of digestion are transferred into the
circulatory system through the blood and
lymph vessels.
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Chapter 48
Section 2 Digestive System
Small Intestine, continued
• Absorption, continued
– The surface area of the small intestine is large
due to the presence of many folds within the
lining of the small intestine and the millions of
villi that are also present.
– The surface area is further increased by the
presence of microvilli.
• Microvilli are extensions of the cell
membranes present on the villi.
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Chapter 48
Section 2 Digestive System
Small Intestine, continued
• Absorption, continued
– Nutrients are sent to the correct place by the
lacteals.
• The lacteals are capillaries and tiny lymph
vessels within the villi.
– The lacteals will take the nutrients to either the
liver or the lymph vessels, and then the blood
will take over delivery of the nutrients to the
cells.
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Chapter 48
Section 2 Digestive System
Cross Section of the Small Intestine
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Chapter 48
Section 2 Digestive System
Large Intestine
• Once absorption is complete in the small
intestine, peristalsis will move the remaining
contents into the colon or large intestine.
• The colon has various sections, and all of these
sections work together to finish the absorption of
nutrients and water.
• The colon initiates contractions that move the
material out of the body.
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Chapter 48
Section 2 Digestive System
Large Intestine, continued
• As nutrients and water are absorbed from the
matter in the colon, the matter solidifies into
feces.
• Feces leave the body by passing through the
rectum and the anal canal.
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Chapter 48
Section 2 Digestive System
Absorption of Nutrients in the Intestines
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Chapter 48
Section 3 Urinary System
Objectives
• Identify the major parts of the kidney.
• Relate the structure of a nephron to its function.
• Explain how the processes of filtration, reabsorption,
and secretion help maintain homeostasis.
• Summarize the path in which urine is eliminated from
the body.
• List the functions of each of the major excretory
organs.
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Chapter 48
Section 3 Urinary System
Kidneys
• The kidneys closely monitor the removal of
nitrogenous waste from the body.
• The kidneys are the main organs of the urinary
system and also regulate the chemical
composition of the blood.
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Chapter 48
Section 3 Urinary System
Urinary System
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Chapter 48
Section 3 Urinary System
Kidneys, continued
• Structure
– The renal cortex is the outermost part of the
kidney that filters blood brought by the renal
artery.
– The renal medulla is the inner part of the
kidney that carries urine to the renal pelvis.
– The renal pelvis is a structure at the center of
the kidney that carries urine to the ureter.
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Chapter 48
Section 3 Urinary System
Kidneys, continued
• Structure, continued
– The nitrogenous wastes are initially brought to
the liver as ammonia, which cannot remain in
the body for long without damaging cells. The
liver converts ammonia to urea.
– Urea is the principle nitrogenous product of the
metabolism of proteins. Urea is found in urine
and other body fluids.
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Chapter 48
Section 3 Urinary System
Human Kidney Structure
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Chapter 48
Section 3 Urinary System
Nephrons
• Substances such as toxins, urea, salts, and water
that are removed from the blood by the kidneys
are collectively called urine.
• Urine is made within in the kidneys by nephrons.
• Nephrons are the functional units of the kidneys.
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Chapter 48
Section 3 Urinary System
Nephrons, continued
• At one end of the nephron is the Bowman’s
capsule. The Bowman’s capsule is a cup-shaped
capsule that surrounds a tight ball of capillaries.
• This ball of capillaries filters wastes from the
blood, retains useful molecules, and produces
urine. This ball of capillaries is called a
glomerulus.
• The nephron and the capillaries of the circulatory
system work closely together to remove wastes
from the blood.
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Chapter 48
Section 3 Urinary System
Nephrons, continued
• Once the blood has been filtered, the material
filtered out flows to the renal tubule.
• The renal tubule includes three parts: the
proximal convoluted tubule, the loop of Henle,
and the distal convoluted tubule.
• The blood still in the glomerulus travels through a
bed of capillaries and to the renal vein.
• The three major processes that take place in the
nephron are filtration, reabsorption, and
secretion.
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Chapter 48
Section 3 Urinary System
Parts of a Nephron
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Chapter 48
Section 3 Urinary System
Filtration
• Filtration is the process of separating dissolved
substances, such as impurities in the blood, by
passing them through a porous material.
– Filtration occurs between the glomerulus and
the Bowman’s capsule in the nephrons of a
kidney.
– Filtration occurs because the blood in the
glomerulus is under high pressure.
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Chapter 48
Section 3 Urinary System
Reabsorption and Secretion
• The process of reabsorption allows the body to
retain many of the substances that were removed
from the blood by filtration.
– Most reabsorption occurs in the proximal
convoluted tubule, but some can occur in the
distal convoluted tubule.
• In the distal convoluted tubule, some substances
pass from the blood into the filtrate through a
process called secretion.
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Chapter 48
Section 3 Urinary System
Reabsorption and Secretion, continued
• Formation of Urine
– The fluid and wastes that remain in the distal
convoluted tubule form urine.
– The urine is further concentrated in the
collecting duct by the osmosis of water
through the wall of the duct. This process
allows the body to conserve water.
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Chapter 48
Section 3 Urinary System
Formation of Urine
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Chapter 48
Section 3 Urinary System
Reabsorption and Secretion, continued
• The Loop of Henle
– The loop of Henle is a long U-shaped part of a
nephron that reabsorbs water and salts from
the urine.
– The loop of Henle uses osmosis to further
concentrate urine.
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Chapter 48
Section 3 Urinary System
Nephron Processes
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Chapter 48
Section 3 Urinary System
Waste Substances and Excretion Sites
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Chapter 48
Section 3 Urinary System
The Excretory Organs
• The kidneys, lungs, and skin are all excretory organs.
– The kidneys are the primary excretory organs and play a
vital role in maintaining the homeostasis of body fluids.
– The lungs are the primary site of carbon dioxide
excretion and carry out detoxification and excretion of
volatile substances.
– The skin excretes nitrogen waste, water, and some salts
through perspiration.
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Chapter 48
Section 3 Urinary System
Excretory System
in the Human Body
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Chapter 48
Standardized Test Prep
Multiple Choice
1. What is the primary function of carbohydrates?
A. to aid in digestion
B. to break down molecules
C. to regulate the flow of chyme
D. to supply the body with energy
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Chapter 48
Standardized Test Prep
Multiple Choice, continued
1. What is the primary function of carbohydrates?
A. to aid in digestion
B. to break down molecules
C. to regulate the flow of chyme
D. to supply the body with energy
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Chapter 48
Standardized Test Prep
Multiple Choice, continued
2. How can dehydration best be prevented?
F. by perspiring
G. by inhaling water
H. by drinking water
J. by not drinking water
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Chapter 48
Standardized Test Prep
Multiple Choice, continued
2. How can dehydration best be prevented?
F. by perspiring
G. by inhaling water
H. by drinking water
J. by not drinking water
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Chapter 48
Standardized Test Prep
Multiple Choice, continued
3. Why is the epiglottis important?
A. It regulates the flow of chyme.
B. It prevents food from going down the trachea.
C. It separates the pharynx from the nasal cavity.
D. It is the passage through which food travels to the
stomach.
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Chapter 48
Standardized Test Prep
Multiple Choice, continued
3. Why is the epiglottis important?
A. It regulates the flow of chyme.
B. It prevents food from going down the trachea.
C. It separates the pharynx from the nasal cavity.
D. It is the passage through which food travels to the
stomach.
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Chapter 48
Standardized Test Prep
Multiple Choice, continued
Use the graph to the right
to answer question 4.
The graph shows the
approximate length of
time food spends in
each digestive organ.
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Chapter 48
Standardized Test Prep
Multiple Choice, continued
4. Bile breaks up large fat droplets. Approximately how
long is the food in the digestive tract before it comes
into contact with bile?
F. 4 hours
G. 7 hours
H. 11 hours
J. 13 hours
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Chapter 48
Standardized Test Prep
Multiple Choice, continued
4. Bile breaks up large fat droplets. Approximately how
long is the food in the digestive tract before it comes
into contact with bile?
F. 4 hours
G. 7 hours
H. 11 hours
J. 13 hours
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Chapter 48
Standardized Test Prep
Multiple Choice, continued
Complete the following analogy:
5. lung : alveolus :: kidney :
A. ureter
B. nephron
C. microvillus
D. glomerulus
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Chapter 48
Standardized Test Prep
Multiple Choice, continued
Complete the following analogy:
5. lung : alveolus :: kidney :
A. ureter
B. nephron
C. microvillus
D. glomerulus
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Chapter 48
Standardized Test Prep
Multiple Choice, continued
Use the figure below to answer
question 6. The figure
shows a cross section of a
kidney.
6. Which part of the
model represents the
loop of Henle?
F. 1
G. 2
H. 3
J. 4
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Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 48
Standardized Test Prep
Multiple Choice, continued
Use the figure below to answer
question 6. The figure
shows a cross section of a
kidney.
6. Which part of the
model represents the
loop of Henle?
F. 1
G. 2
H. 3
J. 4
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Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 48
Standardized Test Prep
Short Response
The liver and pancreas are accessory organs of the
gastrointestinal tract.
In what two ways do the liver and pancreas differ
from other digestive organs?
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Chapter 48
Standardized Test Prep
Short Response, continued
The liver and pancreas are accessory organs of the
gastrointestinal tract.
In what two ways do the liver and pancreas differ
from other digestive organs?
Answer: Both the pancreas and the liver play major
roles in other organ systems. They do not lie in
the gastrointestinal tract, but they release their
secretions into it.
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Chapter 48
Standardized Test Prep
Extended Response
Base your answers to parts A & B on the information below.
When a person’s kidneys stop functioning, urea builds up in the
blood. For the urea to be removed, the person must be
attached to a mechanical kidney, also called a dialysis
machine.
Part A What would happen if the person did not have the urea
removed from his or her blood?
Part B Using your understanding of how a normal kidney
functions, suggest a design for the major components of a
dialysis machine.
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Chapter 48
Standardized Test Prep
Extended Response, continued
Answer:
Part A Urea would build up in the blood.
Because urea is toxic, a build up of urea would
likely make a person sick.
Part B The machine must be able to take the
unfiltered blood away from the body, filter the
blood, regulate the fluid balance and
concentration, and then return the filtered
blood back to the body.
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